1983 FIAT UNO battery

6On 999, 1108 and 1372 cc engines, the
distributor is driven from the rear end of the
camshaft.
7On the 1116 and 1299/1301 cc engines, the
distributor is driven from an extension of the
oil pump driveshaft which is geared to the
auxiliary shaft.
8The distributor contains a reluctor mounted
on its shaft, and a magnet and stator fixed to
the baseplate.
9Ignition advance is controlled in the
conventional way mechanically by centrifugal
weights and a diaphragm unit for vacuum
advance.
10Instead of the conventional method of
interrupting the low tension circuit to generate
high tension voltage in the coil by means of a
mechanical contact breaker, when the
electronic ignition is switched on, the
switching of the transistors in the electronic
control unit (ECU) prevents current flow in the
coil primary windings.
11Once the crankshaft rotates, the reluctor
moves through the magnetic field created by
the stator and when the reluctor teeth are in
alignment with the stator projections a small
AC voltage is created. The ECU amplifies this
voltage and applies it to switch the transistors
and so provide an earth path for the primary
circuit.
12As the reluctor teeth move out of
alignment with the stator projections the AC
voltage changes, the transistors in the ECU
are switched again to interrupt the primary
circuit earth path. This causes a high voltage
to be induced in the secondary winding.
Distributor
(breakerless type) -
removal and refitting
#
13Removal of the distributor on the 903,1116, 1299 and 1301 cc engines is as
described in Chapter 4, Section 6.
14On 999, 1108 and 1372 cc engines, mark
the position of the distributor clamp plate in
relation to the cylinder head surface.
15Unclip the distributor cap and move it to
one side with the HT leads attached.
16Disconnect the LT lead plug and, where
applicable, the vacuum hose (photo).
17Unscrew the distributor fixing nuts and
withdraw the unit.
18The distributor drive is by means of an
offset dog no special procedure is required to
refit it. Providing the dog engages in its slot
and the distributor body is turned to align the
marks made before removal, the timing will
automatically be correct.
19If a new distributor is being fitted (body
unmarked), set No. 4 piston at TDC (0º) by
turning the crankshaft pulley bolt until the
timing marks on the crankshaft pulley and
engine front cover are in alignment.
20Align the drive dog and fit the distributor
then turn the distributor body until the contact
end of the rotor is aligned with the arrow on
the distributor dust shield.
21Tighten the distributor clamp nuts. Refit the
cap and disconnected components and then
check ignition timing using a stroboscope.
Distributor (breakerless
type) - overhaul#
22It is recommended that a worn out or
faulty distributor is renewed. However,
individual components such as the cap, rotor,
reluctor, magnet/stator/baseplate assembly,
vacuum diaphragm unit, and drive gear or dog
are available separately.
Breakerless
ignition system
components - testing
ª
23A voltmeter and an ohmmeter will be
required for this work.
Primary circuit voltage
24Turn on the ignition, and using a voltmeter
check the voltage at the ignition coil LT
terminals. Any deviation from battery voltage
will indicate a faulty connection, or if these are
satisfactory, then the coil is unserviceable.
Magnetic impulse generator winding
25Remove the distributor and ECU and
disconnect their connecting leads.
26Connect an ohmmeter to the impulse
generator terminals and note the reading. The
resistance should be as given in the Specifi-
cations at the beginning of this Chapter.
27Now check between one of the impulse
generator terminals and the metal body of the
distributor. Infinity should be indicated on the
ohmmeter. If it is not, renew the impulse
generator carrier plate. Note: When carrying out
this test it is imperative that the connections are
remade as originally observed. Also ensure that
there is no possibility of the ECU supply (red)
cable and earth cable making contact in service.
Ignition coil winding resistance
28Check the resistance using an ohmmeter
between the coil LT terminals. Refer to the
Specifications for the expected coil resistance.
29Check the resistance between the LT lead
socket on the coil and each of the LT
terminals. Refer to the Specifications for the
expected coil resistance.
30The rotor arm resistance should be
approximately 5000 ohms.
Microplex ignition system -
description
31This system is fitted to the 1301 and
1372 cc Turbo ie models, and comprises the
following components.
Electro-magnetic sensors
32Two sensors are used to pick up engine
speed and TDC position directly from the
crankshaft.
Pressure and vacuum sensor
33This converts inlet manifold vacuum
pressure into an electrical signal for use by
the electronic control unit (ECU).
Anti-knock sensor
34This converts “pinking” detonations which
occur within the combustion chambers into
an electrical signal for use by the ECU (photo).
Electronic Control Unit (ECU)
35This computes the optimum ignition
advance angle from the sensor signals
received, and controls the action of the
ignition unit (photo).
13•86 Supplement: Revisions and information on later models
Fig. 13.72 Rotor aligned with arrow on
distributor dust shield - 999 and 1108 cc
engines (Sec 10)
1 ECU
2 Ignition coil
3 Distributor
4 Vacuum advance
unit5 Pick-up filter with
calibrated opening
for atmospheric
pressure
Fig. 13.71 Location of electronic ignition
components on early models with
breakerless ignition (Sec 10)
10.16 Distributor LT lead connecting plug

Supplement: Revisions and information on later models 13•87
13
10.35 Ignition ECU on rear bulkhead
(1301 cc Turbo ie engine)
Fig. 13.76 Microplex ignition system components on the 1372 cc Turbo ie engine (Sec 10)
Fig. 13.75 Microplex ignition system components on the 1301 cc Turbo ie engine (Sec 10)
1 ECU
2 Safety pressure switch
3 Ignition unit and coil4 Distributor
5 Anti-knock sensorS1 TDC sensor
S2 Engine speed sensor
1 Battery
2 Ignition switch
3 Ignition coil with
control unit
4 ECU
5 Distributor
6 Anti-knock sensor
7 Air pressure
switch
8 Engine speed
sensor
9 TDC sensor
10 Tachometer 10.34 Anti-knock sensor

TDC sensor
48Insert the probes of the ohmmeter
between terminals 1 and 2 of the multipin
connector; 618 to 748 ohms (1301 cc) or 578
to 782 ohms (1372 cc) should be indicated.
49If necessary, carry out a check of the gap
between the sensor and the crankshaft pulley,
as described in Chapter 4, Section 10.
ECU supply
50Switch on the ignition, and then insert the
probes of a voltmeter between terminals 13
and 11 of the multipin connector. Battery
voltage should be indicated. If not, check the
battery earth, ignition switch or intermediate
connector plug for security.
Power module supply (1301 cc)
51Pull the multipin plug from the powermodule, and connect the probes of a
voltmeter between terminal 4 of the connector
and earth. If the reading is less than battery
voltage, check the security of all connections
between the ignition switch and terminal + 15
of the ignition coil.
52Reconnect the multipin connector to the
ECU, but have the one from the power
module disconnected, and then switch on the
ignition.
53Connect the voltmeter between terminals
4 and 2 of the power module multipin
connector. If the indicated voltage is less than
battery voltage, check the security of all
connections between the ignition switch and
terminal + 15 of the ignition coil, and the
battery earth. If all are satisfactory, check for
continuity between terminals 11 and 12. If
continuity is broken, renew the ECU.
Power module (1372 cc)
54Proceed as described in paragraph 53.
Anti-knock sensor
55If “pinking” occurs, or loss of power is
noticed, test the sensor by substitution of a
new one.
Ignition coil
56Disconnect the leads from terminals 1
and 15 on the coil before testing.
57Using the ohmmeter, check the resistance
of the primary winding. This should be
between 0.31 and 0.37 ohms (1301 cc) or
0.40 to 0.49 ohms (1372 cc), at an ambient
temperature of 20ºC (68ºF).
58The secondary winding resistance should
be between 3330 and 4070 ohms (1301 cc) or
4320 to 5280 ohms (1372 cc), at an ambient
temperature of 20ºC (68ºF).
Distributor
59Check the resistance of the rotor arm,
which should be between 800 and
1200 ohms.
60Where all the foregoing tests have proved
satisfactory, then any problem must be due to
a fault in either the power module or the ECU.
These components can only be checked by
the substitution of a new unit - power module
first, then the ECU.
Safety pressure switch
61The device protects the engine from
excessive turbocharging pressure, cutting off
the ignition by earthing the Microplex ECU.
Testing is not possible without a special
pressure pump, so the easiest way to check a
suspected fault is to fit a new unit.
Digiplex 2 ignition system -
description
62This system operates in a similar manner
to that of the earlier type described in Chap-
ter 4, but the circuit layout differs to suit the
Mono Jetronic fuel injection system. In
operation, the main difference is that the
Digiplex 2 system has a greater number of
13•90 Supplement: Revisions and information on later models
Fig. 13.81 Microplex ignition system
control unit connection (Sec 10)
For colour code, see main wiring diagramsFig. 13.80 Microplex ignition system ECU multipin connector (Sec 10)
For colour code, see main wiring diagrams
Fig. 13.79 Ignition advance curves - Microplex ignition system on the 1301 cc Turbo ie
(Sec 10)

advance points than the earlier system.
Comparison of Fig. 13.82 with Fig. 4.2
illustrates the difference in layout. Note that
the distributor is mounted on the rear end of
the cylinder head and is driven by the
camshaft.
63When working on the Digiplex 2 ignition
system or associated components, the
precautionary notes outlined in Section 9 of
Chapter 4 must be adhered to.
64As with the earlier system, test
procedures possible on the Digiplex 2 system
are restricted due to the need for specialised
testing equipment. The following checks are
possible, however, using a conventional test
meter.
Ignition coil check
65To check the resistance of the coil’s
primary windings, connect the probes of an
ohmmeter between the positive terminal and
the negative terminal as shown in Fig. 13.83,
and check that the resistance reading at 18 to
28ºC is 0.45 ohms ± 10% (photo).66To check the resistance of the coil’s
secondary windings, connect the probes of an
ohmmeter between the positive terminal and
the HT lead terminal as shown in Fig. 13.84.
Check that the resistance reading at 18 to
28ºC (64 to 82ºF) is 4800 ohms ± 10%.
Ignition timing check
67Refer to paragraph 2 in this Section.
Engine speed and TDC sensor check
68To check the resistance between the
sensor and the ECU, detach the wiring
connector (photo). Connect the probes of an
ohmmeter to the connector terminals and
check that the resistance reading is between
600 and 760 ohms at 20ºC (68ºF). If the
reading is not as specified, the sensor must
be renewed.
69The gap between the sensor and the pins
on the rear face of the flywheel must be
between 0.2 and 0.8 mm. Any deviation
outside of this clearance will be due to
mechanical damage to the sensor andnecessitates its renewal. The sensor is
accurately positioned during manufacture and
secured with tamperproof screws; it does not
require any adjustment during servicing. If it is
necessary to renew the sensor, a special gap
setting tool is required and the task is
therefore best entrusted to a FIAT dealer.
Supplement: Revisions and information on later models 13•91
Fig. 13.82 Digiplex 2 ignition system wiring circuits and components (Sec 10)
10.68 ECU location on the 1372 cc ie
engine10.65 Ignition coil and connections on the
1372 cc ie engineFig. 13.84 Test connections for ignition
coil secondary windings check - Digiplex 2
ignition system (Sec 10)
Fig. 13.83 Test connections for ignition
coil primary windings check - Digiplex 2
ignition system (Sec 10)
13
1 Connection point (lines connected to
the intake manifold)
2 ECU
3 Ignition coil
4 Distributor
5 Engine flywheel (with
five pins)
6 On/off switch (if fitted)
for advance reduction
7 On/off switch 2 (if fitted)
for curves
8 Battery
9 Spark plugs
10 Tachometer
11 Diagnostic socket
12 Engine speed and TDC sensor
13 To check actuator idle speed
14 To terminal no. 1 of injection control unit
(rpm signal)

require maintenance other than general
inspection for wear in the linkage joints. If
excessive wear is found in any of the joints, they
can be individually detached and renewed.
13Access to the control rods is eased by
detaching and lowering the exhaust system
from the exhaust manifold.
14If a new adjustable control rod is to be
fitted, remove the original rod as a unit, but do
not alter its adjustment for length. The new
rod can then (if required) be set to the same
length as the original in order to maintain the
original setting. Do so by loosening off the
locknut and turning the balljoint as required;
ensure that the angle of the joint is correct
before tightening the locknut.
15Access to the gear lever/main connecting
rod joint from above is made by prising back
the gear lever gaiter from the centre console.
Access from underneath can be made by
raising and supporting the car on axle stands.
Working from the underside of the lever, undo
the retaining nuts and remove the inspection
plate from the floor (photos).
16Any adjustment to the gear linkage should
be entrusted to a FIAT dealer.
Transmission -
removal and refitting#
17The transmission can be removed
together with the engine and then separated
as described in Section 7, or on its own (as
described below), leaving the engine in
position in the car. Before starting to remove
the transmission, it should be noted that
suitable equipment will be required to support
the engine during this procedure.
18Disconnect the battery negative lead.
19Remove the bonnet as described in
Chapter 12.
20Refer to Section 11 in this Chapter for
details and detach the clutch operating
cylinder together with its mounting bracket
from the top of the transmission, but do not
disconnect the hydraulic fluid hose from the
cylinder connection. Leave the cylinder
attached to the bracket. Tie the cylinder and
bracket up to support them out of the way.
21Reaching down between the transmission
and the bulkhead, unscrew the knurled
retaining nut and withdraw the speedometer
cable from the transmission.
22Remove the front roadwheel trims, then
loosen off the front wheel retaining bolts.
Raise the vehicle and support it on axle
stands at a suitable height to allow working
underneath and eventual transmission
removal from under the front end.
23Drain the transmission oil as described
previously in this Section.
24Disconnect and remove the starter motor
(photos).
25Detach the reversing light switch lead
connector.
26Undo the retaining bolt and detach the
earth lead from the rear end of the
transmission (see photo 7C.33). Refit the bolt
once the lead has been disconnected.
13•96 Supplement: Revisions and information on later models
12B.15B Access cover to gear lever lower
connection to rod on the 1372 cc engine
Fig. 13.92 Exploded view of the gear selector and control road assembly components
fitted to 1372 cc models (Sec 12)
12B.15A Gear lever connection to the main
connecting rod on the 1372 cc engine
Fig. 13.91 Exploded view of the gear selector lever, rod and linkage components on
1372 cc models (Sec 12)

Vacuum servo unit and master
cylinder - general
54Access to the vacuum servo unit and the
master cylinder can only be obtained after the
cooling system expansion tank has been
released and moved aside (photo).
Antiskid system - description
55This system is available as an option on
the Turbo ie models only.
56The purpose of the system is to prevent
the wheel(s) locking during heavy brake
applications. This is achieved by automatic
release of the brake on a roadwheel which is
about to lock up, after which the brake is
re-applied. This cycle is carried out many
times per second under heavy braking,
retaining full steering control to avoid any
hazards.
57The main components of the system are
shown in Fig. 13.102. The control module
processes the signals received from the
sensors, and compares them with
deceleration values of the roadwheel and the
slip values of the tyre, which are stored in the
module memory.
58When reference values are exceeded and
wheel lock is imminent, the control module
signals the pressure modulators, which in turn
decrease the brake hydraulic pressure.
59Vehicle road speeds are also taken into
account by the module’s electronic circuits.
60In order to retain optimum system
performance, the tyres and wheels shouldalways be of the type originally fitted by the
vehicle manufacturer.
61Maintenance of the system should be
limited to checking the security of all electrical
and hydraulic connections. Individual compo-
nents are not repairable, and must be
renewed complete if faulty.15 Electrical system
Alternator (999 and
1108 cc models) -
removal and refitting
Á
1To remove the alternator from 999 cc
engine models, disconnect the leads from the
terminals on its rear face.
2Extract the screws and remove the plastic
drivebelt guard.
3Slacken the mounting and adjuster bolts,
push the alternator in towards the engine and
remove the drivebelt.
4Remove the mounting and adjuster bolts,
and withdraw the alternator downwards
through the gap between the right-hand
driveshaft and the engine sump pan (photo).
5Refitting is a reversal of removal; re-tension
the drivebelt.
Alternator (later models) -
removal and refitting Á
6Disconnect the battery negative lead.
7Loosen off the right-hand front roadwheelbolts, then raise and support the car at the
front end on axle stands. Remove the
right-hand roadwheel.
8Remove the wheel arch underwing shield
by driving the compression pins from the
centre of the retaining clips (using a 2 mm
drift), then prise free the panel retaining clips
and remove the shield. Keep the pins and
clips in a safe place and renew any that may
have been damaged during removal (photo).
9Detach the wiring connector from the
alternator.
10Release the alternator mounting and belt
adjuster link bolts, and take off the drivebelt.
11Take out the alternator top and bottom
mounting bolts.
Supplement: Revisions and information on later models 13•103
15.4 Removing the alternator from the
999 cc engine
Fig. 13.102 Braking system on Turbo ie Antiskid models (Sec 14)
13
1 Electronic control unit
(ECU)
2 Roadwheel speed
sensors
3 Pressure modulators
4 Vacuum reservoir
5 Check valve
6 Air cleaner
7 Load proportioning
(pressure regulating)
valves
8 Vacuum switch
9 ECU relay
10 System fault warning
lamp relay
11 System fault warning
lamp
12 Brake stop lamp
switch

15.23A Starter motor removal from the
1301 cc Turbo ie engine15.20 Starter motor removal from the
999 cc engine
12Disconnect the air cooling hose from the
rear cover of the alternator, and then unscrew
the fixing nuts and take off the rear cover with
hose spout. Mark the position of the cover on
the alternator before removing it, so that the
spout will be correctly positioned when
refitted (photos).
13Unbolt the driveshaft bearing
support/alternator bracket from the engine
crankcase, and swivel the support
downwards to provide space for withdrawal of
the alternator (photo).
14Withdraw the alternator from under the
right-hand front wing (photo).
15Refit in the reverse order of removal. Refit
the drivebelt and ensure correct engagement
with the pulleys, then set the drivebelt tension
and tighten the alternator retaining nuts.Alternator brushes -
renewal#
16Depending on model, the brush holder is
secured by two screws, which should be ex-
tracted and the brush holder removed (photos).
17New brushes and the holder are supplied
as an assembly.
Starter motor
(999 cc models) -
removal and refitting
Á
18To remove the starter motor from 999 and
1108 cc models, first disconnect the leads
from the starter motor terminals.
19Release the washer fluid reservoir flexible
bag from the engine compartment rear
bulkhead and move it to the left-hand side.
20Unscrew the starter motor mountingbolts, withdraw the starter from the flywheel
bellhousing, and then lift it out of the left-hand
side of the engine compartment (photo).
21Refitting is a reversal of removal.
Starter motor (1301 cc Turbo ie,
1372 cc ie,
1372 cc Turbo ie) -
removal and refitting
Á
22Disconnect the battery. Working from
under the front end of the car, unscrew the
starter motor mounting bolts and disconnect
the electrical leads.
23Withdraw the starter motor downwards. On
Turbo models, there is just enough clearance, if
the oil cooler hose and the oil pressure switch
lead are deflected carefully aside (photos).
24Refit by reversing the removal operations.
13•104 Supplement: Revisions and information on later models
15.16B Removing the alternator brush
holder
15.16A Extracting the alternator brush
holder screw15.14 Withdrawing the alternator15.13 Driveshaft bracket swivelled
downwards
15.12B Alternator rear cover and fixing nut15.12A Alternator air cooling hose15.8 Remove the wheel arch lower guard
panel for access to the alternator

Starter motor brushes
(later models) - renewal#
25When renewing the starter motor brushes
on later models, the old brushes will need to
be crushed (in a vice or with a hammer) and
their leads then soldered to the new brushes.
Fuses - later models
26The fuse arrangement is slightly different
on later models, but the circuits protected are
still identified by a symbol. Refer to the
Specifications Section for full details. Note
also the terminal block with plastic cover,
which can be used to isolate the battery from
the electrical system by disconnecting the
leads from the terminals (photos).
Relays (Turbo ie models) -
general
27On Turbo ie models, the relays mounted
in the fuse block are as shown in Fig. 13.103.
Additional relays are located as follows:
Headlamp relay - on lead under main fuse
blockFuel injection system main control relay -
adjacent to airflow meter
Headlamps later models
28The headlamp units fitted on later models
differ according to model, but the bulb and
unit replacement details are generally the
same as described for previous models in
Chapter 9. Note that the rubber cover can
only be fitted with the tab to the top as shown
(photo).
Headlamp beam adjusters for
load compensation - later
models
29Some later models are fitted with
headlamp beam adjusters which allowtemporary resetting to be made (such as
when the car is fully loaded). Access to these
adjusters is made by lifting the bonnet (photo).
30Turn the adjusters anti-clockwise to lower
the beam to the normal level or clockwise to
raise the beam (when the car is unloaded).
Repeat the procedure on the opposite
headlamp unit an equal amount.
31Other later models have separate
horizontal and vertical beam adjusters,
positioned as shown (photos). A load
compensating lever is attached to the
adjusters to enable temporary resetting of the
headlamp beams, without changing the
normal adjustment. Turn the lever to the
appropriate side (right or left) to make the
adjustment as required. The normal setting
Supplement: Revisions and information on later models 13•105
15.26B Battery lead terminal block on the
1301 cc Turbo ie model15.23B Starter motor and wiring
connections on the 1372 cc ie engine
15.31B Headlamp vertical beam alignment
adjuster screw on a 1372 cc ie model. Note
the load compensator lever which is set in
the “O” (normal load) setting position15.31A Headlamp horizontal beam
alignment adjuster screw on a 1372 cc ie
model
15.29 Headlamp beam adjuster on the
999 cc Turbo ie model15.28 Headlamp unit fitted to the 1372 cc ie
model
15.26A Fuse block on the 1301 cc Turbo ie
model
13
Fig. 13.103 Auxiliary fuses and relays on
1301 cc Turbo ie models (Sec 15)
1 Horn relay
2 Heated rear screen relay
3 Foglamps relay
4 Radiator fan relay
5 Electric windows relay
6 Foglamps fuse
7 Radiator fan second speed fuse
8 Fuel injector fan fuse
9 Electric windows fuse
10 Electric fuel pump fuse